CN107304782B

CN107304782B - Connecting rod for internal combustion engine

Info

Publication number: CN107304782B
Application number: CN201710263495.0A
Authority: CN
Inventors: 米哈伊尔·伊加科夫
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2016-04-20
Filing date: 2017-04-20
Publication date: 2021-06-11
Anticipated expiration: 2037-04-20
Also published as: DE102017107054A1; CN107304782A; US10018220B2; US20170307005A1

Abstract

A connecting rod for an internal combustion engine is disclosed. The engine has a connecting rod with a large end sized such that the lower surface height is a function of the upper surface height, the face-to-face width, and the belt height and width. The first and second bearing shells are received by the big end under a specified clamping load to form a convex axial profile in response to the big end size, and the crankshaft crankpin interfaces with the convex axial profile. A method of assembling a connecting rod comprising: inserting an upper bearing shell and a lower bearing shell into a large end having a lower surface height that is a function of the upper surface height, the face-to-face width, and the band portion height and the band portion width, wherein each shell has a straight axial profile and a uniform cross-section in a free state, and tightening the cap with a specified load to form a convex axial profile of the upper and lower bearing shells.

Description

Connecting rod for internal combustion engine

Technical Field

Various embodiments relate to a connecting rod for an internal combustion engine.

Background

Connecting rods may be used to connect pistons in internal combustion engines to a crankshaft to convert translational motion of the pistons into rotational motion of the crankshaft. A bearing is disposed between the connecting rod and the crankshaft and has a contoured surface that interfaces with a surface of the crankshaft. The contoured surface of the bearing can affect the performance and function of the bearing. Currently, the profile surface is controlled by expensive and time consuming machining processes performed on the crankpin journal and/or the bearing shell profile.

Disclosure of Invention

In an embodiment, a method of assembling a connecting rod is provided. The upper and lower bearing shells are inserted into the large end with a lower surface height that is a function of the upper surface height, the face-to-face width, and the band portion height and the band portion width, the upper and lower bearing shells each having a straight axial profile and a uniform cross-section in a free state. The cover is tightened at a specified load to form a convex axial profile of the upper and lower bearing shells.

In another embodiment, a connecting rod for an engine has a large end connected to a small end by a beam. The large end defines an aperture and has an upper portion and a lower portion provided by a cover. The upper portion has a shank extending from the beam between first and second upper surfaces adjacent a periphery of the upper portion of the bore. The cap has a band portion between first and second lower surfaces adjacent a periphery of a lower portion of the aperture. The large end has a particular cross-sectional profile wherein the lower surface height is a function of the upper surface height, the lower face-to-face width, the strap portion height and the strap portion width. The upper bearing shell is received by an upper portion of the bore and the lower bearing shell is received by a lower portion of the bore. The first and second fasteners connect the cover to the upper portion of the large end with a specific load. The particular cross-sectional profile of the large end is configured to deform each bearing shell from a free-form, uniform cross-section to a convex axial profile cross-section having a central region of the inner surface at least one micron higher than an edge region of the inner surface in response to securing a cap to an upper portion of the large end with a predetermined load.

In yet another embodiment, an engine has a connecting rod with a large end sized such that a lower surface height is a function of an upper surface height, a face-to-face width, and a belt height and a belt width. The first bearing shell and the second bearing shell are received by the large end under a specified clamping load to form a convex axial profile in response to the large end size. The crankshaft has a crankpin that interfaces with the convex axial profile.

Drawings

FIG. 1 illustrates a schematic diagram of an engine configured to implement the disclosed embodiments;

FIG. 2 shows an exploded view of a connecting rod according to an embodiment;

3A, 3B and 3C show three axial profiles of the surface of the bearing shell in the connecting rod;

FIG. 4 shows a partial front view of the connecting rod of FIG. 2 assembled;

FIG. 5 shows a partial cross-sectional view of the connecting rod of FIG. 2 after assembly;

FIG. 6 shows a partial perspective view of the link of FIG. 2 after assembly.

Detailed Description

As required, detailed embodiments of the present disclosure are provided herein; however, it is to be understood that the disclosed embodiments are merely exemplary and may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present disclosure.

Fig. 1 shows a schematic internal combustion engine 20. The engine 20 has a plurality of cylinders 22, one of which is shown. The engine 20 may include a plurality of cylinders arranged in various ways, including an inline configuration and a V-configuration. The engine 20 has a combustion chamber 24 associated with each cylinder 22. The cylinder 22 is formed by a cylinder wall 32 and a piston assembly 34. The piston assembly 34 is connected to a crankshaft 36. Combustion chamber 24 is in fluid communication with an intake manifold 38 and an exhaust manifold 40. Intake valve 42 controls flow from intake manifold 38 into combustion chamber 24. An exhaust valve 44 controls flow from combustion chamber 24 to exhaust manifold 40.

Fuel injector 46 delivers fuel from the fuel system directly into combustion chamber 24 so the engine is a direct injection engine. Engine 20 may use a low pressure or high pressure fuel injection system, or in other examples, a port injection system. The ignition system includes a spark plug 48, and the spark plug 48 may be controlled to provide energy in the form of a spark to ignite the fuel-air mixture in the combustion chamber 24. In other embodiments, other fuel delivery systems and ignition systems or techniques (including compression ignition) may be used. Intake and

exhaust valves

42, 44, injector 46, and spark plug 48 may be operated in various ways known in the art to control engine operation.

The engine 20 includes a controller and various sensors configured to provide signals to the controller for controlling air and fuel delivery to the engine, spark timing, power and torque output from the engine, and the like. The engine sensors may include, but are not limited to, an oxygen sensor in exhaust manifold 40, an engine coolant temperature sensor, an accelerator pedal position sensor, an engine manifold pressure (MAP) sensor, an engine position sensor for crankshaft position, an air mass sensor in intake manifold 38, a throttle position sensor, and the like.

In some embodiments, the engine 20 is used as the sole prime mover in a vehicle (such as a conventional vehicle or a stop-start vehicle). In other embodiments, the engine may be used in a hybrid vehicle, wherein an additional prime mover (such as an electric machine) is adapted to provide additional power to propel the vehicle.

Each cylinder 22 operates in a four-stroke cycle that includes an intake stroke, a compression stroke, an ignition stroke, and an exhaust stroke. In other examples, the engine may operate using a two-stroke cycle. During the intake stroke, the intake valve 42 is opened and the exhaust valve 44 is closed while the piston assembly 34 moves from the top of the cylinder 22 to the bottom of the cylinder 22 to introduce air from the intake manifold into the combustion chamber. The position of the piston assembly 34 at the top of the cylinder 22 is commonly referred to as Top Dead Center (TDC). The position of the piston assembly 34 at the bottom of the cylinder is commonly referred to as Bottom Dead Center (BDC).

During the compression stroke, the intake valve 42 and the exhaust valve 44 are closed. The piston 34 moves from the bottom to the top of the cylinder 22 to compress the air in the combustion chamber 24.

The fuel is then introduced into the combustion chamber 24 and ignited. In the illustrated engine 20, fuel is injected into the combustion chamber 24 and then ignited using the spark plug 48. In other examples, the fuel may be ignited by a compression ignition process.

During the expansion stroke, the ignited fuel-air mixture in the combustion chamber 24 expands, moving the piston 34 from the top of the cylinder 22 to the bottom of the cylinder 22. Movement of the piston assembly 34 causes a corresponding movement of the crankshaft 36 and provides a mechanical torque output of the engine 20. The combustion process that causes the expansion stroke generates a load and force on the engine 20. The force on the engine caused by the combustion event in combustion chamber 24 exerts a force on face 50 of piston 34, and at least a portion of this force is transmitted down connecting rod 52 to crankshaft 36.

Connecting rod 52 is connected to a crank pin 54 or crank pin journal of crankshaft assembly 36. Crankpin 54 is connected to a crankshaft 56 or main bearing journal of crankshaft assembly 36 via a web 58 such that crankpin 54 is offset from the main bearing journal of crankshaft 56. The crankshaft assembly may also include counterweights extending from the web structure 58 to rotationally balance the crankshaft assembly. The main bearing journal 56 is supported for rotation by a main bearing disposed, for example, in the engine block or crankcase. The opposite end of the connecting rod 52 is connected to the piston 34, for example, by a wrist pin 60 or wrist pin and associated bearings.

During the exhaust stroke, the intake valve 42 remains closed and the exhaust valve 44 is opened. Piston assembly 34 moves from the bottom of cylinder 22 to the top of cylinder 22 to expel exhaust gases and combustion products from combustion chamber 24 by reducing the volume of combustion chamber 24. Exhaust flows from the combusting cylinders 22 to an exhaust manifold 40 and then to an aftertreatment system (such as a catalytic converter).

The position and timing of the intake and

exhaust valves

42, 44, as well as the fuel injection and ignition timing, may be controlled and/or varied for each engine stroke and for various engine operating conditions and loads.

The engine 20 has a cylinder block 70 forming a cylinder 22. The cylinder head 72 is connected to the cylinder block 70. The cylinder head 72 surrounds the combustion chamber 24 and also supports the

various valves

42, 44 and the intake and

exhaust systems

38, 40. A cylinder head gasket or other sealing member may be disposed between the cylinder block 70 and the cylinder head 72 to seal the combustion chamber 24.

Fig. 2 shows an exploded view of the connecting rod 100. In one example, connecting rod 100 is used as connecting rod 52 in engine 20.

Connecting rod 100 has a large end 102 connected to crank pin or crank journal 54 and an opposite small end 104 connected to piston pin or wrist pin 60. The large end 102 and the small end 104 are connected by a pole segment 106 or beam 106. The small end 104 defines an aperture 108, the aperture 108 being sized to receive the wrist pin 60 and any associated bearings. The large end 102 defines a bore 110, the bore 110 being sized to receive the crank pin 54 and associated bearings.

Connecting rod 100 may be formed as a single, unitary component, for example, by a forging process. After forming the connecting rod 100, the large end 102 may be split or broken, as shown, to provide a bearing cap 112 that is connected to the main body 114 of the connecting rod or the remainder 114 of the connecting rod. Thus, when the connecting rod 100 is disassembled, the large end 102 and the bore 110 are divided into two separate portions, a first or upper portion 116 of the bore 110 being formed by the body 114 and a second or lower portion 118 of the bore 110 being formed by the bearing cap 112.

The cover 112 is connected to the body 114 by fasteners 140. For example, each fastener 140 may be a bolt or a nut and bolt assembly. The big end 102 of the connecting rod defines a hole, such as a threaded hole, a through hole, or a blind hole, that receives the fastener 140. The cover 112 and the body 114 each define a portion of each aperture for receiving a fastener 140. The fasteners 140 are disposed on opposite sides of the aperture 110.

The bearing assembly 120 is disposed within the bore 110 of the big end 102 of the connecting rod. The bearing assembly 120 has an upper housing 122 and a lower housing 124. The upper housing 122 is received by the upper portion 116 of the bore 110. The upper portion 116 of the aperture 110 defines a surface having an associated radius of curvature or radius, and the surface has a profile shaped as a portion of a circle (e.g., a semi-circle). The upper housing 122 of the bearing assembly 120 is shaped with an associated radius of curvature or radius such that the profile of the upper housing 122 is also a portion of a circle (e.g., a semi-circle). The radius of curvature of the upper housing 122 is greater than the radius of curvature of the upper portion 116 of the bore 110. Thus, the end 126 of the upper shell 122 extends slightly beyond the end of the upper portion 116 of the bore, or slightly beyond the parting line 128 or break line of the large end 102.

The lower portion 118 of the aperture 110 defines a surface having an associated radius of curvature or radius, and the surface has a profile shaped as a portion of a circle (e.g., a semi-circle). The lower portion 118 of the bore has the same radius of curvature or radius as the upper portion 116 of the bore. The lower housing 124 of the bearing assembly 120 is shaped with an associated radius of curvature or radius such that the profile of the lower housing 124 is also a portion of a circle (e.g., a semi-circle). In one example, the radius of curvature or radius of the lower shell 124 is the same as the radius of curvature or radius of the upper shell 122. The radius of curvature of the lower housing 124 is greater than the radius of curvature of the lower portion 118 of the bore 110. Thus, the end 130 of the lower housing 124 extends slightly beyond the end of the lower portion of the hole, or slightly beyond the separation line 128 or break line of the lid.

To form the connecting rod 100, a rod preform is provided as an integral unit or as a single piece, for example, in a forging or like process. The rod preform may now be machined, for example, to provide a hole for the fastener 140 and/or to machine the wall surface of the hole 108 to the relevant specifications. The rod preform is then split, for example, in a cracking process along break line 128 to provide body 114 and cover 112. After splitting, the cover 112 is connected to the body 114 using the fasteners 140 and applying a specified torque rating thereto. The bore 110 is then machined to relevant specifications, for example, using a line bore process, to form the surfaces of the upper 116 and lower 118 portions of the bore wall. Machining the hole 110 after the cracking process provides a more controlled and uniform hole wall surface.

Then, after the hole 110 is machined, the fastener 140 is removed or loosened so that the cap 112 is removed from the main body 114 of the connecting rod. An upper bearing shell 122 and a lower bearing shell 124 are inserted into the upper portion 116 and the lower portion 118, respectively, of the bore 110. Each of the

ends

126, 130 of the upper and

lower shells

122, 124 extend beyond the break or separation line 128 or, when inserted, extend beyond or protrude from the ends of the upper and lower portions 116, 118 of the bore. The cover 112 is then reconnected to the body 114 using the fasteners 140 and applying a specified nominal torque thereon, which in turn causes the upper and lower portions 116, 118 of the bore 110 to contact the

respective bearing shells

122, 124 and the bearing assembly 120 to be radially compressed by the bore wall 110. The protruding end 126 of the upper bearing shell 122 and the protruding end 130 of the lower bearing shell 124 contact each other and may be deformed when the bearing is pressed.

Thus, the surrounding bore wall 110 applies stress to the bearing assembly 120. In the installed state, the bearing assembly 120 is subjected to hoop or circumferential stresses in the tangential direction due to the radial or compressive forces exerted on the bearing assembly 120 by the surrounding linkage 100 structure. The bearing assembly 120 is also subjected to axial and radial stresses; however, these forces are small compared to hoop stress based on the thin-walled, open structure of the bearing assembly 120. This hoop stress serves to locate and retain the bearing

shells

122, 124 within the connecting rod bore 110.

Fig. 3A-3C show three examples of axial profiles of the inner diameter of a bearing shell of a bearing assembly. The axial profile is taken along the axis of the bearing shell into the page of figures 3A to 3C. Fig. 3A shows a flat or straight first axial profile 150 of the bearing shell. In one example, the straight axial profile is provided by a bearing shell having a uniform cross-sectional profile (e.g., a rectangle having a constant width and thickness along the length of the bearing shell). A flat or straight axial profile on the surface of the bearing housing that interfaces with the crankpin journal has a surface that deforms less than 1 micron in the axial direction. The flat profile 150 in fig. 3A represents the bearing shell profile in a free form when the bearing shell is unloaded or in a free state, or after the bearing shell is inserted into the connecting rod and bore wall 152 and before it is compressed by it. Note that the bearing shell in fig. 3A has a uniform cross section or a uniform thickness.

When the bearing assembly 120 is inserted into the bore 110 of the connecting rod and the fastener 140 is tightened to a particular torque rating, the bearing assembly 120 experiences hoop stress when compressed by the bore 110 of the connecting rod. The bearing assembly 120 is subject to bearing crushing and radial crushing loads, deforming the bearing shell.

When used in connecting rod 100, the axial profile of bearing assembly 120 is directly related to the performance and function of the bearing. Previously, the axial profile of a bearing assembly was not controlled, or controlled by performing a precision machining (precision machining) process on the surface of the crankpin or journal in addition to standard machining (for shaping the cylindrical surface of the journal of the crankpin). Any machining performed on the crankpin journal is a precision machining process and is therefore time consuming and expensive. In some cases, it is not sufficient to control the axial profile of the crankpin journal, and other axial profiles must be introduced into the bearing shell, for example by providing the bearing shell with a non-flat axial profile before it is loaded or by machining the bearing shell after assembly into the connecting rod.

A concave axial profile 160 is shown in fig. 3B. This concave axial profile 160 is the final profile that is common in conventional connecting rod systems without precision machining of the journal or machining of the axial profile of the bearing shell prior to insertion into the connecting rod. The concave axial profile has a height 162, wherein a central region of the axial profile is concave or below the edges of the bearing shell and results from deformation of the bearing shell based on hoop stress and strain applied from the bore wall 164. A concave axial profile may be defined as having a central region that is concave by more than one micron relative to the edge of the bearing shell and has a concave axial curvature. Note that the hole wall 164 represents a hole wall according to a conventional connecting rod.

The flat or straight axial profile 150 in fig. 3A can be set to the final axial profile of the bearing assembly under load, for example, after a precision machining process, and have a target circumferential profile (eccentricity, crush relief, etc.). In another example, the flat axial profile 150 may be provided using a connecting rod according to the present disclosure described below without a post-assembly machining process.

A convex axial profile 170 is shown in fig. 3C. Since the crankpin journal bends under load during engine operation, this can result in contact along the edge of the bearing shell for a flat or concave profile (as shown in fig. 3A and 3B), and thus the convex axial profile 170 is the desired axial profile of the bearing assembly 120 when loaded. The convex axial profile 170 of fig. 3C provides a more robust shape for the bearing assembly 120 because it allows the crank pin 54 and its journal surface to flex without loading, rubbing or wear along the edges of the bearing shell. In another example, the connecting rod 100 described below in accordance with the present disclosure is used to provide the convex axial profile 170 without post-assembly machining of the crank pin journal surface and/or the bearing housing. The height 172 of the axial profile 170 is defined as the distance the central region of the axial profile 170 rises above the edge of the bearing shell. A convex axial profile may be defined as having a central region that rises more than one micron above the edge of the bearing shell and has a convex axial curvature. In a further example, the height 172 may be defined to be in a range of one to three microns.

Fig. 4-6 illustrate partial views of large end 102 and bearing assembly 120 of connecting rod 100 according to the present disclosure. Elements that are the same or similar to those shown in fig. 2 are assigned the same reference numerals. In one example, the connecting rod may be connecting rod 100 for engine 20. The plan view of the linkage 100 as shown in fig. 4 may be associated with both sides of the linkage such that the shape of the linkage is the same on either side. In some examples, specific details of the connecting rod (e.g., lubricant passages) may be present on only one side, or may be positioned differently on each side.

Based on the function of the various features of the connecting rod and the relationship therebetween, the structure of the connecting rod 100 itself is controlled to a particular size such that the large end 102 has a specified shape and the bearing

shells

122, 124 have a predetermined axial profile 170 under a clamping load or a specified load when the connecting rod is assembled and the fastener is tightened. The overall dimensions of the connecting rod itself are controlled such that the convex axial profile 170 of the bearing

shells

122, 124 is provided by the surrounding structure of the connecting rod 100, performing only a straight boring process on the bore wall 110 and having the bearing

shells

122, 124 with a flat or straight axial profile and uniform thickness prior to insertion of the connecting rod and in a free state via compression of the bearing shells. This eliminates any precision machining of the journal or bearing shell axial profile.

The connecting rod 100 and bearing assembly 120 of fig. 4-6 have a controlled overall structure, shape and size to produce a convex axial profile 170 of the bearing

shells

122, 124 as shown in fig. 3C when using bearing

shells

122, 124 having a straight axial profile in an unloaded state such as that shown in fig. 3A.

A clamping load is generated around the bearing

shells

122, 124 by tightening the fasteners 140 to provide bearing compression. During bearing compression, the bearing

shells

122, 124 deform based on the contact pressure or force between the bearing

shells

122, 124 and the surrounding linkage structure. The body 114 and the cover 112 of the connecting rod 100 also have small deformations due to bearing compression. Deformation of the bearing

shells

122, 124, the main body 114 of the connecting rod, and the cover 112 of the connecting rod generates strain energy within these components. The strain energy associated with the bolt clamping load is used to hold or maintain the bearing

shells

122, 124 in place within the bore 110 of the connecting rod. The force balance of the strain energy of the connecting rod 100 and the bearing

shells

122, 124 deforms the bearing shells such that the shape of the bearing

shells

122, 124 is not uniform and a convex profile 170 is created. Note that each bearing

shell

122, 124 used in the present disclosure has a constant thickness and a flat or straight axial profile 150 (an example of which is shown in fig. 3A) prior to assembly into the connecting rod and in an unloaded or free state.

The connecting rod 100 has various features whose size and shape are controlled such that when the bearing

shells

122, 124 are squeezed and the connecting rod 100 and bearing

shells

122, 124 are deformed, the final deformed shape of the inner diameter of the bearing shells has a desired convex axial profile 170 or cylindrical profile. The connecting rod 100 according to the present disclosure achieves the desired convex axial profile 170 of the bearing

shells

122, 124 via the shape features of the connecting rod 100 structure without any precision machining of the bearing

shells

122, 124 surfaces and/or crankshaft journal surfaces. The shape characteristics of the connecting rod 100 are specifically defined in the design of the shape of the large end 102 and are formed in a forging process or other connecting rod forming process or by roughing and do not require any special or additional machining or manufacturing processes to be performed on the connecting rod 100, thus providing a more robust bearing system 120 for the connecting rod 100 and reducing or eliminating additional machining and manufacturing processes, time and costs.

The dimensions of link thrust surfaces 180, 182 and body shank 184 and cover band (strap)186 are controlled relative to each other to control the final axial profile 170 of bearing assembly 120. Structural features of the link 100 that control deformation of the bearing

shells

122, 124, including dimensions of the link thrust surfaces 180, 182, the fillet radius (fillet radii)188 between the thrust surface 180 and the associated link shank 184, and the fillet radius 190 between the thrust surface 182 and the cover tape portion 186, are shown and described below with reference to fig. 4-6.

The beam 106 of the connecting rod has an i-beam structure including a narrow central member 192 having an axial width a and two outer cross members 194 extending from the central member 192. The shank 184 or upper portion 116 of the large end 102 of the link extends from the beam 106 and has an axial width B that is approximately equal to the width B of the outer cross member 194 of the beam. An upper surface 180 or upper thrust surface 180 is provided on each side of a shank 184 of the large end 102 and around the periphery of the upper region of the bore 110. The axial distance C or axial width C between the opposing upper surfaces 180 of the connecting rods is greater than the axial width B of the large end shank 184. A radius 188 or fillet 188 is provided between the shank 184 and the upper surface 180 to provide stress distribution and the necessary draft angle for forming the connecting rod 100. The upper surface 180 has a surface width D extending radially outward from the aperture wall 110.

The cover 112 of the connecting rod has a band 186. The band 186 is configured to have an axial width E and a height F defined as the distance between the lower bore wall 110 and the outer surface of the band. A lower surface 182 or lower thrust surface 182 is provided on each side of the cover 112 and surrounds the periphery of the lower region of the aperture. The distance C between the opposing lower surfaces 182 of the links corresponds to the distance C between the opposing upper surfaces 180 such that the upper and

lower surfaces

180, 182 on the same side are coplanar with one another. The axial distance C or axial width C between the opposed lower surfaces of the tie rods is greater than the axial width E of the band portion of the cap. A radius 190 or fillet is provided between the band 186 and the lower surface 182 to provide stress distribution and the necessary draft angle for forming the tie rod. The lower surface 182 has a surface width G extending radially outward from the bore wall.

A channel 196 or groove for lubricant flow may be provided on one of the upper surface 180 and the lower surface 182 on at least one side of the connecting rod.

To provide a convex axial profile 170 of the bearing assembly under load according to the present disclosure, the following relationships are provided for various dimensions of the connecting rod 100.

The relationship between the height (G) of the lower surface 182 and the axial width (E) of the band 186 is: g < E.

The relationship between the axial width (E) of the band 186 and the face-to-face axial width (C) is: 0.2C < E < 0.6C.

The relationship between the height (G) of the lower surface 182 and the face-to-face axial width (C) is: 0.2C < G < 0.6C. It is therefore noted that the relationship between the height (G) of the lower surface 182, the axial width (E) of the band 186, and the face-to-face axial width (C) is: 0.2C < G < E < 0.6C.

The relationship between the height (G) of the lower surface 182 and the height (F) of the strap 186 is: 0.2F < G < 0.5F.

The relationship between the height (D) of the upper surface 180 and the height (G) of the lower surface 182 is: d < 0.8G.

According to one example, the connecting rod 100 uses a bearing assembly 120 having bearing

shells

122, 124 having a straight axial profile 150 and a uniform thickness when in an unloaded, pre-assembled state as shown in FIG. 3A, and shaped according to the above relationship. The bearing

shells

122, 124 have an axial width of about 20 millimeters and a thickness of about 1.5 millimeters to 2.5 millimeters. The fastener 140 is tightened to a predetermined torque rating thereby introducing clamping loads, strains, deformations and bearing compression of the connecting rod 100 and bearing assembly 120. When the fastener 140 is tightened, the surface 128 on the connecting rod 100 is axially deformed to have a convex profile as shown in FIG. 5, which in turn deforms the bearing

shells

122, 124 to the desired convex axial profile as shown. Prior to deformation, the surface 128 has a straight or linear axial profile due to the straight boring process used in manufacturing the connecting rod assembly 100.

The profile of the final bearing assembly 120 or

housing

122, 124 is a convex axial profile 170 having a height on the order of one micron or more, although a range of heights between zero and three microns is contemplated.

Of course, in other embodiments, the connecting rod 100 and bearing shells 122, 124 (for example) may be otherwise sized for use in various engines while maintaining the dimensional relationship via the connecting rod 100 structure and the strain created by tightening the fastener 140 to a predetermined torque level to provide the convex axial profile 170 of the bearing assembly 120 within the spirit and scope of the present disclosure.

While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosure. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. Furthermore, features of various implemented embodiments may be combined to form further embodiments of the disclosure.

Claims

1. A method of assembling a connecting rod, comprising:

inserting an upper bearing shell and a lower bearing shell into a large end, the large end having a lower surface height that is a function of an upper surface height, a face-to-face width, and a band portion height and a band portion width, the upper and lower bearing shells each having a straight axial profile and a uniform cross-section in a free state;

the cover is tightened at a specified load to form a convex axial profile of the upper and lower bearing shells.

2. The method of claim 1, further comprising: the upper and lower bearing shells are each deformed from a free state to a convex axial profile in response to securing the cover to the connecting rod at the specified load.

3. The method of claim 2, wherein the function between the lower surface height G, the belt portion width E, and the face-to-face width C is: 0.2C < G < E < 0.6C;

wherein the function between the lower surface height G and the upper surface height D is: d < 0.8G;

wherein the function between the lower surface height G and the strap portion height F is: 0.2F < G < 0.5F.

4. The method of claim 2, wherein the function between the lower surface height G, the belt portion width E, and the face-to-face width C is: 0.2C < G < E < 0.6C.

5. The method of claim 2, wherein the function between the lower surface height G and the upper surface height D is: d < 0.8G.

6. A method according to claim 2, wherein the function between the lower surface height G and the strap portion height F is: 0.2F < G < 0.5F.

7. The method of claim 2, further comprising:

splitting the large end to form the remainder of the cap and link;

the cap is fastened to the rest of the connecting rod and the large end is bored straight.

8. The method of claim 7, further comprising: separating the cover from the remainder of the linkage;

wherein, the following steps are sequentially executed: forming a connecting rod, splitting the large end, fastening the cover and linearly boring the large end, separating the cover, inserting the upper and lower bearing shells and fastening the cover with the specific load.

9. The method of claim 1, further comprising connecting the big end of the connecting rod around a crankpin of the crankshaft, the crankpin being formed as a cylindrical journal.

10. The method of claim 1, wherein the center of the convex axial profile has a height of up to three microns formed by the specific load and function induced deformation.

11. A connecting rod for an engine, comprising:

a large end connected to the small end by a beam, the large end defining a bore and having an upper portion and a lower portion provided by a cap, the upper portion having a shank extending from the beam, the shank being located between first and second upper surfaces adjacent a periphery of the upper portion of the bore, the cap having a band portion located between first and second lower surfaces adjacent the periphery of the lower portion of the bore; the large end having a particular cross-sectional profile wherein the lower surface height is a function of the upper surface height, the lower face-to-face width, the strap portion height and the strap portion width;

an upper bearing shell received by an upper portion of the bore and a lower bearing shell received by a lower portion of the bore;

a first fastener and a second fastener for connecting the cover to the upper portion of the large end with a specific load;

wherein the specific cross-sectional profile of the large end is configured to: in response to securing the cap to the upper portion of the large end with a predetermined load, both the upper bearing shell and the lower bearing shell are deformed from a free-form uniform cross-section to a convex axial profile cross-section having a central region of the inner surface at least one micron higher than an edge region of the inner surface.

12. The connecting rod of claim 11, wherein the function between the lower surface height G, the band width E, and the following to surface width C is: 0.2C < G < E < 0.6C;

13. The connecting rod of claim 11, wherein the function between the lower surface height G, the band width E, and the following to surface width C is: 0.2C < G < E < 0.6C.

14. The connecting rod of claim 11, wherein the function between the lower surface height G and the upper surface height D is: d < 0.8G.

15. The connecting rod of claim 11 wherein the function between the lower surface height G and the strap portion height F is: 0.2F < G < 0.5F.

16. The connecting rod of claim 11, wherein the bore of the large end is formed as a cylinder having a first radius;

wherein each of the upper and lower bearing shells has a second radius greater than the first radius in an unloaded state.

17. An engine, comprising:

a link having a large end sized such that the lower surface height is a function of the upper surface height, the face-to-face width, and the strap portion height and the strap portion width;

first and second bearing shells received by the large end under a specified clamping load to form a convex axial profile in response to the large end size;

a crankshaft having a crank pin interfacing with the convex axial profile.

18. The engine of claim 17, wherein the crankpin has a cylindrical outer journal surface to interface with the convex axial profile of each of the first and second bearing shells.

19. The engine of claim 17, wherein each of the first and second bearing shells has a straight axial profile and a uniform cross-section in a free state.

20. An engine according to claim 17, wherein the function between the lower surface height G, the belt portion width E and the face-to-face width C is: 0.2C < G < E < 0.6C;